Liquid crystal display devices have been applied in a wide range of fields from large display devices such as TV sets to small display devices such as mobile phones, and those with higher added value have been developed. In recent years, in view of rising interest in the global environment and improvement of the convenience of mobile devices, development of liquid crystal display devices with low power consumption has attracted attention.
For example, Patent Document 1 discloses a technique for reducing the power consumption of a liquid crystal display device, according to which all of the signal lines are electrically disconnected to a signal line driver circuit to have high impedance in order to keep the voltage of each signal line constant in a break period during which no scan line and no signal line are selected.
Non-Patent Document 1 discloses a structure for reducing the power consumption of a liquid crystal display device, according to which the refresh rate is made to be different in the case of moving image display and in the case of still image display. Non-Patent Document 1 further discloses a technique for preventing fluctuation of a voltage applied to a liquid crystal element in order to prevent a flicker due to the fluctuation of the voltage applied to the liquid crystal element, which is accompanied by switching of a signal between a break period and a scan period in the case where a still image is displayed, according to which AC signals with the same phase are applied to a signal line and a common electrode also in the break period.